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KVM: arm64: Enable access to sanitized CPU features at EL2

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Introduce the infrastructure in KVM enabling to copy CPU feature
registers into EL2-owned data-structures, to allow reading sanitised
values directly at EL2 in nVHE.

Given that only a subset of these features are being read by the
hypervisor, the ones that need to be copied are to be listed under
<asm/kvm_cpufeature.h> together with the name of the nVHE variable that
will hold the copy. This introduces only the infrastructure enabling
this copy. The first users will follow shortly.

Signed-off-by: Quentin Perret <qperret@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20210319100146.1149909-14-qperret@google.com
This commit is contained in:
Quentin Perret 2021-03-19 10:01:21 +00:00 committed by Marc Zyngier
parent 8e17c66249
commit 7a440cc783
5 changed files with 59 additions and 0 deletions
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1
arch/arm64/include/asm/cpufeature.h
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@ -607,6 +607,7 @@ void check_local_cpu_capabilities(void);
u64 read_sanitised_ftr_reg(u32 id);
u64 __read_sysreg_by_encoding(u32 sys_id);
int copy_ftr_reg(u32 id, struct arm64_ftr_reg *dst);
static inline bool cpu_supports_mixed_endian_el0(void)
{

22
arch/arm64/include/asm/kvm_cpufeature.h Normal file
View File

@ -0,0 +1,22 @@
/* SPDX-License-Identifier: GPL-2.0-only */
/*
* Copyright (C) 2020 - Google LLC
* Author: Quentin Perret <qperret@google.com>
*/
#ifndef __ARM64_KVM_CPUFEATURE_H__
#define __ARM64_KVM_CPUFEATURE_H__
#include <asm/cpufeature.h>
#include <linux/build_bug.h>
#if defined(__KVM_NVHE_HYPERVISOR__)
#define DECLARE_KVM_HYP_CPU_FTR_REG(name) extern struct arm64_ftr_reg name
#define DEFINE_KVM_HYP_CPU_FTR_REG(name) struct arm64_ftr_reg name
#else
#define DECLARE_KVM_HYP_CPU_FTR_REG(name) extern struct arm64_ftr_reg kvm_nvhe_sym(name)
#define DEFINE_KVM_HYP_CPU_FTR_REG(name) BUILD_BUG()
#endif
#endif

4
arch/arm64/include/asm/kvm_host.h
View File

@ -740,9 +740,13 @@ void kvm_clr_pmu_events(u32 clr);
void kvm_vcpu_pmu_restore_guest(struct kvm_vcpu *vcpu);
void kvm_vcpu_pmu_restore_host(struct kvm_vcpu *vcpu);
void setup_kvm_el2_caps(void);
#else
static inline void kvm_set_pmu_events(u32 set, struct perf_event_attr *attr) {}
static inline void kvm_clr_pmu_events(u32 clr) {}
static inline void setup_kvm_el2_caps(void) {}
#endif
void kvm_vcpu_load_sysregs_vhe(struct kvm_vcpu *vcpu);

13
arch/arm64/kernel/cpufeature.c
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@ -1154,6 +1154,18 @@ u64 read_sanitised_ftr_reg(u32 id)
}
EXPORT_SYMBOL_GPL(read_sanitised_ftr_reg);
int copy_ftr_reg(u32 id, struct arm64_ftr_reg *dst)
{
struct arm64_ftr_reg *regp = get_arm64_ftr_reg(id);
if (!regp)
return -EINVAL;
*dst = *regp;
return 0;
}
#define read_sysreg_case(r) \
case r: val = read_sysreg_s(r); break;
@ -2773,6 +2785,7 @@ void __init setup_cpu_features(void)
setup_system_capabilities();
setup_elf_hwcaps(arm64_elf_hwcaps);
setup_kvm_el2_caps();
if (system_supports_32bit_el0())
setup_elf_hwcaps(compat_elf_hwcaps);

19
arch/arm64/kvm/sys_regs.c
View File

@ -21,6 +21,7 @@
#include <asm/debug-monitors.h>
#include <asm/esr.h>
#include <asm/kvm_arm.h>
#include <asm/kvm_cpufeature.h>
#include <asm/kvm_emulate.h>
#include <asm/kvm_hyp.h>
#include <asm/kvm_mmu.h>
@ -2775,3 +2776,21 @@ void kvm_sys_reg_table_init(void)
/* Clear all higher bits. */
cache_levels &= (1 << (i*3))-1;
}
#define CPU_FTR_REG_HYP_COPY(id, name) \
{ .sys_id = id, .dst = (struct arm64_ftr_reg *)&kvm_nvhe_sym(name) }
struct __ftr_reg_copy_entry {
u32 sys_id;
struct arm64_ftr_reg *dst;
} hyp_ftr_regs[] __initdata = {
};
void __init setup_kvm_el2_caps(void)
{
int i;
for (i = 0; i < ARRAY_SIZE(hyp_ftr_regs); i++) {
WARN(copy_ftr_reg(hyp_ftr_regs[i].sys_id, hyp_ftr_regs[i].dst),
"%u feature register not found\n", hyp_ftr_regs[i].sys_id);
}
}